In magnetic recording, as one example of a type of recording in which reading and writing are performed by a head that moves relative to the surface of the storage medium, data may be written in circular tracks on a magnetic disk. To read data on a given track, the read head may be centered on that particular track. However, sometimes the read head may deviate from its ideal path and stray “off-track,” with part of the head over the “main track” (i.e., the track to be read) and part of the head over an adjacent track. In such a case, the read-back signal produced at the read head is a superposition of a signal from the main track and a signal from the adjacent track.
In addition, in order to increase recording density, it has become common to write tracks very close to each other. There is even a technique known as “shingled recording” in which adjacent tracks overlap one another. In such cases, the width of the read head may be greater than the track pitch (i.e., the distance between adjacent tracks) which results in a contribution from one or more adjacent tracks in the read-back signal for the main track of interest.
The contribution from an adjacent track presents similar challenges whether it results from small track pitch, in which case it may be referred to as “inter-track interference” (ITI), or from an off-track condition in which case it may be referred to as “off-track interference” (OTI).